The Shared Causal Pasts and Futures of Cosmological Events
The Shared Causal Pasts and Futures of Cosmological Events
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DOI：
10.1103/physrevd.88.044038
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发表时间：
2013-05
影响因子：
5
通讯作者：
A. Friedman;D. Kaiser;J. Gallicchio
中科院分区：
文献类型：
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作者：
A. Friedman;D. Kaiser;J. Gallicchio
我们推导了两个宇宙事件是否可以有一个共同的因果过去或共同的因果未来的标准，假设一个具有普朗克卫星最适合的\Lambda CDM宇宙学参数的弗里德曼-勒梅特-罗伯逊-沃克宇宙。我们进一步推导出两个宇宙事件是否在热“大爆炸”（我们认为这是早期宇宙膨胀的结束）之后与我们自己的世界线有过因果联系的标准。我们发现，红移为z >= 3.65的类星体等天体对彼此之间或与我们过去的世界线之间没有共同的因果关系。如果从地球上看，这些物体彼此之间的红移不同，或者出现的相对角度小于180度，则会有更复杂的限制。我们提出了观测到的类星体对的例子，这些类星体对满足过去因果独立性的全部、部分或全部标准。考虑到暗能量和最近的加速膨胀，我们可观测到的宇宙有一个有限的共形寿命，因此宇宙事件视界在当前红移z = 1.87。因此，我们限制了成对的宇宙事件是否能在时间终结之前发出彼此世界线的信号。最后，我们推广了具有非零空间曲率的FLRW宇宙共享过去和未来因果域的准则。
We derive criteria for whether two cosmological events can have a shared causal past or a shared causal future, assuming a Friedmann-Lemaitre-Robertson-Walker universe with best-fit \Lambda CDM cosmological parameters from the Planck satellite. We further derive criteria for whether either cosmic event could have been in past causal contact with our own worldline since the time of the hot "big bang", which we take to be the end of early-universe inflation. We find that pairs of objects such as quasars on opposite sides of the sky with redshifts z >= 3.65 have no shared causal past with each other or with our past worldline. More complicated constraints apply if the objects are at different redshifts from each other or appear at some relative angle less than 180 degrees, as seen from Earth. We present examples of observed quasar pairs that satisfy all, some, or none of the criteria for past causal independence. Given dark energy and the recent accelerated expansion, our observable universe has a finite conformal lifetime, and hence a cosmic event horizon at current redshift z = 1.87. We thus constrain whether pairs of cosmic events can signal each other's worldlines before the end of time. Lastly, we generalize the criteria for shared past and future causal domains for FLRW universes with nonzero spatial curvature.